1. Field of the Invention
This invention relates to a back light module, particularly to one formed with a multi-layer structure and having the outer side of its frame body and back board provided with numerous radiating fins and radiating grains for increasing the heat-dissipating area of the back light module, having excellent effect in heat dissipation.
2. Description of the Prior Art
A conventional back light module, as shown in FIG. 1, is formed with a multi-layer structure, which is composed from bottom to top of a reflecting sheet, a light-guiding plate, a diffusing plate and a prism sheet. The light-guiding plate has its peripheral side installed with cold cathode fluorescent lamps (CCFL) and light emitting diodes (LED) and its bottom surface provided with reflecting net points. This multi-layer structure is engaged in an outer frame and then mounted on a bottom board to make up the back light module. The light-guiding plate of the conventional back light module is disposed with a mirror surface, and the diffusion plate and the prism sheet are respectively bored with through holes for presenting the mirror surface of the light-guiding plate.
The conventional back light module is provided with the mirror surface, and the CCFLs or the LEDs installed at the peripheral side of the light-guiding plate as a light source to be scattered by the reflecting net points at the bottom surface of the light-guiding plate. And then the light reflected to the topside of the light-guiding plate by the reflecting sheet for reinforcing the lighting at the peripheral side of the mirror surface and increasing irradiation effect on the mirror surface. Generally, the outer frame of the conventional back light module is made of plastic molded in shape to lighten the back light module, and the luminous intensity of the light source has to be elevated for making clear the image on the back light plate. Thus, the heat energy produced by the light source will be relatively heightened and the outer frame will receive a certain extent of heating effect, and since the plastic outer frame has bad effect in heat dissipation; therefore, the CCFLs and LEDs are likely to be damaged due to bad heat dissipation. In addition, only through the light-guiding plate and the diffusion sheet and the prism plate, can the CCFLs and LEDs increase irradiation effect on the mirror; therefore, the conventional back light module needs to increase its structural layers in order to make images clear, thus complicating manufacturing processes.